Bot breaks Hotmail's CAPTCHA in 6 seconds

A new bot can crack defenses erected by Microsoft to keep spammers from creating large numbers of accounts on its Live Hotmail service within seconds, a security researcher said Friday.

Dan Hubbard, vice president of security research at Websense, said the bot broke Live Hotmail's CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart) within six seconds, on average. CAPTCHA is the name given to the distorted, scrambled characters that many Web services require users to decipher and type in to create a new account; the tests are meant to block automated account registration by spammers and malware authors.

The bot, Hubbard acknowledged, is similar to one Websense uncovered in February.

"In the past, though, it was kind of questionable whether the CAPTCHA breaking was automated," Hubbard said Friday, noting that there had been some evidence that spammers were paying people to decode and type in the CAPTCHA characters. "But the bot's breaking [CAPTCHA] in six seconds, so it's definitely automated."

In a long post to the Websense blog Thursday, Sumeet Prasad -- "our CAPTCHA expert," said Hubbard -- provided technical details of how the bot automatically registers Live Hotmail accounts and then immediately begins using those accounts to spew spam.

The bot's total response time -- how long it takes the program to grab a CAPTCHA image, analyze it and return with the correct code -- is considerably shorter than that of earlier such bots, said Prasad in the blog.

One in every eight to 10 attempts to create a Live Hotmail account is successful, added Prasad, meaning that the success rate is 10 per cent to 15 per cent. However, the rate is actually meaningless, said Hubbard, since the bot will continue to try to create accounts using a predetermined list of account names until they're all registered.

Copies of the bot are seeded on unsuspecting users' PCs, said Websense, making it less likely that Microsoft will detect and stop the automated account registrations.

Free Web-based e-mail services such as Live Hotmail, Yahoo Mail and Gmail are favorite targets for spammers because the services' domains can't be blocked by blacklisting antispam tools, Hubbard said. "When Google, Microsoft and Yahoo [domains] are in the top 10 or top 20 spam domains, it's hard to use reputation tools," said Hubbard.

Latest Videos

Hear from Invictus Games Sydney 2019 CEO, Patrick Kidd OBE and Head of Technology, @James-d-smith -share their insights on how they partnered with Unisys to protect critical data over an open, public WiFi solution.

With so much change all the time, how can executives best prepare their businesses to meet the security challenges of the coming years? CSO Australia, in conjunction with Mimecast, explored this question in an interactive Webinar that looks at how the threat landscape has evolved – and what we can expect in 2019 and beyond.

According to new research conducted by the Ponemon Institute, Australia and New Zealand have the highest levels of data breaches out of the nine countries investigated. This was linked to heavy investment in security detection and an under-investment in security and vulnerability response capabilities

Copyright 2018 IDG Communications. ABN 14 001 592 650. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of IDG Communications is prohibited.